During the lowering phase of a biceps curl, which type of muscle action do the elbow flexors perform?

During the lowering phase of a biceps curl, the elbow flexors engage in an eccentric action. Eccentric actions occur when a muscle lengthens while under tension, which is precisely what happens when lowering a weight. In this case, although the elbow flexors (like the biceps brachii) are working to control the descent of the weight, they are lengthening as they do so. This action is critical in managing the load and preventing injury, helping to stabilize the movement while the muscle resists the forces acting upon it.

In contrast, concentric actions involve a muscle shortening while generating force, which is what happens during the upward phase of a biceps curl. Isometric actions occur when a muscle contracts without changing its length, such as when holding a weight steady at a certain point. Isokinetic actions refer to muscle contractions performed at a constant speed, typically using specific equipment that controls the movement’s pace. Therefore, in the context of the lowering phase of a biceps curl, eccentric action is the correct identification of how the elbow flexors are functioning.